Method:

  • Place butter and sugar in the bowl of a mixer and mix on medium for 3 minutes.
  • Scrape down the sides and add the egg yolk and beat well.
  • In another bowl whisk together the flour and cocoa powder.
  • Add to the butter mixture all at once. Then mix in at lowest speed until it just comes together (it will have small and medium clumps). Any more and it will become sticky and difficult to work with.
  • Scrape dough into tart pan. Press into the bottom of the tart and outward using the heel of your palm. Use your fingers to pull the tart up the edge. Chill for an hour in the fridge. Reserve a little bit of dough to patch the shell later if necessary.
  • Preheat the oven to 350F.
  • Bake tart shell for 15 minutes.
  • Check to see if the dough has cracked, if so patch it with the reserved dough. Bake for another 10-15 minutes, keeping an eye on it to ensure it doesn't burn. Cool on wire rack.
  • Make the caramel: In a saucepan, whisk together sugar, corn syrup, and water and bring to a boil. Cook over medium-high heat until a medium-dark amber colour, swirling occasionally. Take off heat and add the cream, butter, and sour cream. Stir together until smooth. Pour into cooled tart shell and let cool to room temperature, then place in the fridge to chill and set.
  • Make the ganache: Bring cream to a boil in a 1-qt. saucepan over medium heat. Put chocolate into a medium bowl and pour in hot cream; let sit for 1 minute, then stir slowly with a rubber spatula until smooth. Pour ganache evenly over tart and refrigerate until set, 4–5 hours.
  • Sprinkle tart with sea salt, slice, and serve chilled.
  • SERVES 8-10.